Steam injection is a standard technique for improving oil recovery from a well. In conventional Steam Assisted Gravity Drainage (SAGD) oil wells, there is a period of well warm up that entails injecting steam down a steam injection string and taking returns in a second string in a dual string configuration. This process is used to place heat into the reservoir in order to decrease viscosity of the bitumen in place, as well as establish communication between the injector and producer.
After the well has warmed up sufficiently and communication between the injector and producer has been established, it is often desirable to inject steam into a well at a location other than the bottom of the tubing. To this end, steam distribution devices through which steam can be injected into the surrounding bore from the steam injection string are often disposed at intervals along the injection string. These distribution devices are run-in in a closed position and maintained in the closed position during circulation in order to efficiently get heat down to the toe of the well and ensure circulation from the toe to the heel can be accomplished.
After a period of weeks/months, it is desirable to stop circulating and start injection of the steam. In order to accomplish this, a coiled tubing shifting tool (such as an Otis B shifting tool) is lowered into the injection string tubing on either coiled tubing or on small diameter tubing with a service rig. The shifting tool is used to open one distribution device at a time so that steam can pass from the central bore of the injection string to the annulus around the string. One disadvantage of these systems is that a coiled tubing unit and shifting tool are required to enter the well to open the valves. This operation introduces additional costs, risks and time compared with the invention proposed.
Some conventional steam splitter designs inject steam into the annulus through nozzles placed at right angles in the wall of the tubing on the injection string. This direct flow against other tubulars can lead to erosion in circumstances where fluid rates are high and liquid is present. Over time, the steam jetting can cut control lines, cut the sand control mechanism of the liner and generally cause wellbore damage.